How much rain in Seattle this week? Millions of tanker trucks' worth

We all know Seattle gets a lot of rain, but have you ever thought of just much water really falls in a big rainstorm?

Local engineer Dale Smith had the burning question pop into his head when he read about a statistic that says our "Pineapple Express" type rain storms transports an amount of water vapor equal to between 7.5 to 15 times the average flow of liquid water out of the Mississippi River.

His quest: How many tanker trucks would it take to haul enough water to cover all of King County with 1 inch of rain -- roughly the amount of total rain expected in the Seattle area through the weekend.

(Start formulating your guesses now)

10,000? A million? A billion?

For his base, he's using the double tankers that you see filling up gas stations -- those carry 8,000 gallons of liquid.